Using 802.11n and WPA2
In order to test 802.11n with consumer hardware we replaced the Linksys WRT-54GL (running OpenWRT) with a Linksys WAP610N. The WAP610N is an access point featuring 802.11a, 802.11b, 802.11g and 802.11n connectivity in dual bands (2.4 GHz and 5 GHz). You cannot mix the two frequencies, but you can run the access point in mixed mode or select one of the 802.11abgn modes. Since we run WPA2 using AES in our office we configured the security configuration as well. And then we connected some clients, one of them being a Lenovo T500 because its WLAN netword card supports 802.11abgn as well. Which data rates can you expect?
First of all you have to understand that we did no benchmarks and no scientifically correct study. We measured some data transmission with very crude tools. The important lesson is that the rate being used by the media interface (the different WLAN modulations or the modes of the PHY in case of wired networks) has nothing to do with the throughput between applications. There's a big difference between layer 1 and layer 7. While we saw that the WLAN NIC uses the 802.11n data rates the overall throughput was between 10 and 20 Mbit/s. This is consistent with the data rates seen with the WRT-54GL. We didn't turn off WPA2 encryption, but we believe that this mode also eats some of the potentiel throughput since the hardware of both access points isn't very powerful in terms of processing power. It's sad to see hardware without cryptographic accelerators, even though the crypto chips are available for a few USD per chip.
Don't get carried away by vendor marketing. Announcements like 300 Mbit/s or more sound fantastic, but in reality a decent wired network connection beats wireless data transmissions most of the time. Wireless network access works best for device that don't need a lot of data, so don't think about using it in your backbone (there are reports of people really doing that).